The invention relates to a calibration apparatus for temperature probes comprising a calibration chamber with an opening for receiving an insert having passages for receiving temperature probes, where the chamber has several heat energy elements, and wherein the apparatus has temperature probes and electric circuits for controlling the heat energy elements.
Such calibration apparatus is known eg from WO 99/04231. Such apparatuses are used for calibrating temperature probes with an accuracy that may be down to 0.01°. Due to the high degree of accuracy there is a number of sources of error, some of which have already been remedied by the prior art. One of the major problems originates in heat being conveyed away from the calibration chamber near the opening. One the one hand due to it not being possible to arrange any heating element in the opening where the insert is to be introduced and, on the other, due to the temperature probe(s) that are arranged in the passages entailing an uncontrollable discharge of heat (or cold), also in case eg the heating elements in the calibration chamber can be controlled for achieving a very precise temperature. The thermal energy from the heating elements is to propagate through the insert, where temperature probes are disposed in some of the passages, but maybe not in all of them; and wherein each of the temperature probes discharges a certain amount of thermal energy to the effect that, precisely where the temperature probe to be calibrated is disposed, the temperature is not at all the same as the temperature of the heating elements. The use of several heat energy elements is a known method of reducing the undesired and unknown temperature gradients, but so far it has only been possible to control the temperature immediately around the heat energy elements.
The object of the invention is to provide a calibration apparatus whereby improved accuracy can be obtained in the calibration of a temperature probe than has been possible so far.